Chelyabinsk

The Chelyabinsk meteorite represents one of the most significant astronomical events of the twenty-first century. At 3:20 UTC on February 15, 2013, a celestial body approximately 20 meters in diameter penetrated Earth's atmosphere above the southern Urals region at a velocity of approximately 19.16 kilometers per second. The aerial explosion generated by its atmospheric impact, which occurred at approximately 23 kilometers altitude, released energy equivalent to 440 kilotons of TNT, roughly 30 times greater than the Hiroshima bomb. The resulting shock wave caused widespread structural damage, injuring over 1,500 people in the city of Chelyabinsk and surrounding areas.

From a mineralogical perspective, the meteorite belongs to the class of ordinary chondrites, subtype H5, characterized by silicate chondrules embedded in a fine matrix rich in iron and nickel. The composition includes olivine (Mg,Fe)₂SiO₄, orthopyroxene (Mg,Fe)SiO₃, plagioclase feldspar, and iron-nickel metallic phases (kamacite and taenite). The thermal metamorphism grade of 5 indicates that the material underwent significant heating in the parent asteroid body prior to fragmentation and fall. The recovered fragments, some weighing several kilograms, provided researchers with a unique opportunity to study the primordial composition of the inner Solar System and the processes of planetary differentiation.

Classification: Ordinary chondrite H5, with thermal metamorphism grade 5 and aqueous alteration grade W0-W1. Primary mineralogical composition: olivine (Fa₁₈₋₂₀), orthopyroxene (Fs₁₆₋₁₈Wo₁₋₂), plagioclase (An₁₂₋₁₅), Fe-Ni metallic phases (kamacite and taenite in approximately 90:10 proportion). Bulk density: 3.3-3.5 g/cm³. Mohs hardness: 5-6 (variable depending on mineralogical phase). Magnetic properties: ferromagnetic due to metallic iron content. Fracture index: irregular; metals display conchoidal fracture. Oxygen isotopic analysis (δ¹⁸O and δ¹⁷O) places the material on the ordinary fractionation line (OC). Radiometric age: approximately 4,560 million years (age of the primitive Solar System), with cosmic ray exposure age estimated at 5-10 million years prior to impact. Raman spectroscopy shows characteristic peaks of olivine, pyroxene, and magnetite. Scanning electron microscopy (SEM-EDS) reveals elemental compositions consistent with H5 type and absence of significant alteration from terrestrial processes.